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<html lang="zh-CN">

<head>
    <meta charset="UTF-8" />
    <title>10_数学对象-案例练习</title>
</head>

<body>
    <script>
        var str = 'qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890';

        var code_str = '';

        for(var i = 0; i < 4; i++){
            var random = Math.floor(Math.random() * 62);
            var code = str[random];
            code_str += code;
        }
        console.log(code_str);








    </script>
</body>

</html>